Ordered Pd₂Ge intermetallic nanoparticles as highly efficient and robust catalyst for ethanol oxidation

Abstract

Pd₂Ge nanoparticles were synthesized by superhydride reduction of K₂PdCl₄ and GeCl₄. The syntheses were performed using a solvothermal method in the absence of surfactants, and the size of the nanoparticles was controlled by varying the reaction time. The powder X-ray diffraction (PXRD) and transmission electron microscopy data suggest that Pd₂Ge nanoparticles were formed as an ordered intermetallic phase. In the crystal structure, Pd and Ge atoms occupy two different crystallographic positions with a vacancy in one of the Ge sites, which was proved by PXRD and energy-dispersive X-ray analysis. The catalyst is highly efficient for the electrochemical oxidation of ethanol and is stable up to the 250^th cycle in alkaline medium. The electrochemical active surface area and current density values obtained, 1.41 cm² and 4.1 mA cm^–2, respectively, are superior to those of the commercial Pd on carbon. The experimentally observed data were interpreted in terms of the combined effect of adsorption energies of CH₃CO and OH radical, d-band center model, and work function of the corresponding catalyst surfaces.